1. Field of the Invention
The present invention relates to a rotary solenoid.
2. Description of the Related Art
Conventionally, a rotary solenoid has been known and disclosed, for example, in a Japanese Patent Application Laid-Open Publication No. 9-154267. The rotary solenoid described in this patent publication as a conventional device has a yoke 90 which is divided into three parts such as a first yoke 91, a second yoke 92, and a core 93 around which a coil is wound as shown in FIG. 8. Then, one end and the other end terminals of the core 93 are fastened to the first yoke 91 and the second yoke 92 using fixation screws 94 and 95, respectively.
In such a structure, two fixation screws 94 and 95 are required for assembling and then the number of part increase is unavoidable. Further, a screw hole for each screw shall be processed and then assembling man-hour increase is also unavoidable. Then, the cost increases due to increase of the number of part and assembling man-hour.
Further, since the positions of the first and second yokes 91 and 92 fluctuate, an air gap (clearance) of a rotor 96 facing them becomes ununiform and then quality and performance will be degraded.
Further, the rotary solenoid described in the above patent application publication as a preferred embodiment, has a yoke 100, which is divided into two parts, a first yoke 101, and a second yoke 102 as shown in FIG. 9. A core is formed, on which the coil is wound around a part of the first yoke 101 and the second yoke 102. Then, thus divided first yoke 101 and the second yoke 102 are fixed by two shaft bearing plates 104 and 105 for pivotally supporting a shaft 103.
However, even if such a structure is employed, the number of part increases and the cost increases. Further, since the first yoke 101 and the second yoke 102 shall be seized by two shaft bearing plates 104 and 105, the size of the rotary solenoid shall be increased.
As another conventional rotary solenoid, the solenoid described in a Japanese Patent Application Laid-Open Publication No. 2000-341927, for example, is also known. The rotary solenoid described in this patent publication includes a pair of right and left yokes and a core, on which the coil is wound around, seized by them. The rotary solenoid is structured by integrally resin-molding both yokes and the core.
However, since both yokes and the core are different parts, their positions may be displaced when they are set in a die for resin-molding. Then, since a contact portion between each yoke and the core is easily displaced, performance is degraded due to a gap caused by this displacement, for example.
Further, if the positions of circular arc portions 51 and 52 of the yoke are displaced, the air gap (clearance) of the rotor becomes ununiform, and then quality and performance are degraded.